Fair Value Measurements (Fair Value Measurement on Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair value measurements of assets on a recurring basis
Investment securities available for sale	$ 742,846	$ 163,134
Recurring
Fair value measurements of assets on a recurring basis
Total	742,846	163,134
Recurring | U.S. Treasury and U.S. Government-sponsored agencies
Fair value measurements of assets on a recurring basis
Investment securities available for sale	21,427	6,039
Recurring | Municipal securities
Fair value measurements of assets on a recurring basis
Investment securities available for sale	173,037	49,060
Recurring | U.S. Government-sponsored agencies
Fair value measurements of assets on a recurring basis
Investment securities available for sale	542,399	108,035
Recurring | Corporate obligations
Fair value measurements of assets on a recurring basis
Investment securities available for sale	4,010
Recurring | Mutual funds and other equities
Fair value measurements of assets on a recurring basis
Investment securities available for sale	1,973
Recurring | Level 1
Fair value measurements of assets on a recurring basis
Total	1,973	0
Recurring | Level 1 | U.S. Treasury and U.S. Government-sponsored agencies
Fair value measurements of assets on a recurring basis
Investment securities available for sale	0	0
Recurring | Level 1 | Municipal securities
Fair value measurements of assets on a recurring basis
Investment securities available for sale	0	0
Recurring | Level 1 | U.S. Government-sponsored agencies
Fair value measurements of assets on a recurring basis
Investment securities available for sale	0	0
Recurring | Level 1 | Corporate obligations
Fair value measurements of assets on a recurring basis
Investment securities available for sale	0
Recurring | Level 1 | Mutual funds and other equities
Fair value measurements of assets on a recurring basis
Investment securities available for sale	1,973
Recurring | Level 2
Fair value measurements of assets on a recurring basis
Total	740,873	163,134
Recurring | Level 2 | U.S. Treasury and U.S. Government-sponsored agencies
Fair value measurements of assets on a recurring basis
Investment securities available for sale	21,427	6,039
Recurring | Level 2 | Municipal securities
Fair value measurements of assets on a recurring basis
Investment securities available for sale	173,037	49,060
Recurring | Level 2 | U.S. Government-sponsored agencies
Fair value measurements of assets on a recurring basis
Investment securities available for sale	542,399	108,035
Recurring | Level 2 | Corporate obligations
Fair value measurements of assets on a recurring basis
Investment securities available for sale	4,010
Recurring | Level 2 | Mutual funds and other equities
Fair value measurements of assets on a recurring basis
Investment securities available for sale	0
Recurring | Level 3
Fair value measurements of assets on a recurring basis
Total	0	0
Recurring | Level 3 | U.S. Treasury and U.S. Government-sponsored agencies
Fair value measurements of assets on a recurring basis
Investment securities available for sale	0	0
Recurring | Level 3 | Municipal securities
Fair value measurements of assets on a recurring basis
Investment securities available for sale	0	0
Recurring | Level 3 | U.S. Government-sponsored agencies
Fair value measurements of assets on a recurring basis
Investment securities available for sale	0	0
Recurring | Level 3 | Corporate obligations
Fair value measurements of assets on a recurring basis
Investment securities available for sale	0
Recurring | Level 3 | Mutual funds and other equities
Fair value measurements of assets on a recurring basis
Investment securities available for sale	$ 0